Recently, the trend to develop a small structure or a thin structure of an electronic device has increased the need for connection between the fine circuit patterns, connection between the fine parts and fine circuit patterns, and so forth. Examples of the conventionally-employed connection methods include a soldering connection technique, a technique employing anisotropic electroconductive adhesive. Furthermore, a method is known in which an anisotropic electroconductive sheet is provided between an electronic device and a circuit board, thereby enabling electronic connection therebetween.
An anisotropic electroconductive sheet is an elastomer sheet which exhibits electroconductivity in a particular direction alone. Examples of anisotropic electroconductive sheets include: an anisotropic electroconductive sheet which exhibits electroconductivity only in the direction perpendicular to the plane of the sheet (i.e., the thickness direction); an anisotropic electroconductive sheet which exhibits electroconductivity only in the thickness direction only in a case in which stress is applied to the sheet in the thickness direction; and so forth.
Such an anisotropic electroconductive sheet enables compact electronic connection without involving soldering, mechanical fitting, and so forth. Furthermore, the anisotropic electroconductive sheet has the advantage of enabling flexible connection while absorbing mechanical shock and distortion. Anisotropic electroconductive sheets having such advantages are widely used in the fields of liquid crystal displays, cellular phones, electronic calculators, electronic digital clocks, electronic cameras, computers, and so forth.
Such an anisotropic electroconductive sheet is also referred to as “elastomer sheet”. Examples of elastomer connectors employing such anisotropic electroconductive sheets include: the alternately-stacked type (which will also be referred to as “alternately-layered type”) elastomer connector having a structure in which electroconductive elastomer sheets and insulating elastomer sheets are alternately stacked; and the enclosure type (which will also be referred to as “sheet-type”) elastomer connector having a structure in which an electroconductive portion is enclosed within an insulating portion, thereby providing the property of exhibiting electroconductivity in the direction perpendicular to the plane of the sheet, while serving as an insulator in the direction along the plane of the sheet.
Such elastomer connectors are widely used as connectors for electrically connecting circuit devices such as a printed board, leadless chip carrier, liquid crystal panel, and so forth, with each other.
FIG. 4 is a perspective view which shows an arrangement in which an enclosure-type elastomer connector employing an anisotropic electroconductive sheet according to conventional techniques is applied to a semiconductor measuring device. In FIG. 4, reference numeral 6 denotes a surface-mounting IC. Reference numeral 7 denotes an anisotropic electroconductive sheet.
As shown in FIG. 4, the IC 6 includes multiple leads 6A extending from the four side faces thereof. On the other hand, multiple contact pins 61 connected to the semiconductor measuring device are disposed so as to face the leads 6A with the anisotropic electroconductive sheet 7 introduced therebetween. The semiconductor measuring device, to which the multiple contact pins 61 are connected, is not shown in the drawing.
In FIG. 4, the anisotropic electroconductive sheet 7 is formed of an insulating elastomer sheet 7A serving as a base. The elastomer sheet 7A has multiple dot-shaped elastomer regions formed so as to enable current to flow between the front face and the back face thereof. The dot-shaped elastomer regions 7B are arranged corresponding to the array of the multiple leads 6A.
As shown in FIG. 4, upon pressing the multiple leads 6A onto the surfaces of the dot-shaped elastomer regions 7B, the multiple measurement contact pins 61 are pressed into contact with the dot-shaped elastomer regions 7B from the back. This electrically connects the multiple contact pins 61 with the multiple leads 6A through the dot-shaped elastomer regions 7B, thereby enabling measurement of the IC 6.
With such an arrangement, measurement is made with the anisotropic electroconductive sheet introduced between the leads of the IC and the measurement contact pins. This enables measurement of the IC without damaging the leads of the IC.
On the other hand, FIG. 5 is a perspective view which shows a conventional arrangement in which an LCD (Liquid Crystal Display) and a control board are connected through an alternately-stacked anisotropic electroconductive sheet. In FIG. 5, reference numeral 8 denotes an LCD, reference numeral 9 denotes an anisotropic electroconductive sheet, and reference numeral 81 denotes a control board for controlling the LCD 8.
In FIG. 5, the anisotropic electroconductive sheet 9 has a layered structure in which thin film electroconductive elastomer sheets 9A and thin film insulating elastomer sheets 9B are alternately stacked. Furthermore, silicon rubber members 9C, which serve as adhesive, are provided to both side faces of the layered structure along the film stacking direction. The anisotropic electroconductive sheet 9 having such a layered structure is provided to both sides of the control board 81.
With such an arrangement, the LCD 8 is mounted on the anisotropic electroconductive sheet 9 using holding means, as shown in FIG. 5. This enables electrodes formed on the LCD 8 at a fine pitch and edge connectors (line connection terminals) formed on the control board 81 at a fine pitch to be connected through the anisotropic electroconductive sheet 9.
A manufacturing method for the anisotropic electroconductive sheet 9 shown in FIG. 5 is known as follows. That is to say, first, an insulating material is applied to metal wires arranged in parallel at a predetermined pitch so as to form a single anisotropic electroconductive block. Then, the anisotropic electroconductive block is thinly sliced in the direction perpendicular to the axes of the metal wires, thereby obtaining the anisotropic electroconductive sheets 9 (See Patent Document 1, for example).    [Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2000-340037